$n_f: 13vw;//底部导航栏
$blue: #4a91ee;
.link_img {
  width: 6vw;
  height: 6vw;
}
//方向，边框，高度，背景颜色, 子元素的width
@mixin nav_box($direction: true, $bor_t: true, $hei: 13vw, $bgd_color: #fff) {
  position: fixed;
  display: flex;
  width: 100vw;
  height: $hei;
  background-color: $bgd_color;
  padding-top: 1vw;
  padding-bottom: 1vw;
  font-size: 1vw;
  z-index: 1000;
  @if $direction {
    bottom: 0;
    @if $bor_t {
      border-top: .5px solid #eee;
    }
  }@else {
    top: 0;
    justify-content: space-between;
    align-items: center;
    @if $bor_t {
      //border-bottom: .5px solid #eee;
    }
  }
  & > * {
    color: #939393;
    @if $direction {
      flex: 1;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    text-align: center
  }
}